Multi-electrode submerged arc welding system

Abstract

To provide proper welding quality by stabilizing feeding variable speed control, in a multi-electrode submerged arc welding system.SOLUTION: In a multi-electrode submerged arc welding system, a plurality of submerged arc welding apparatuses PS1 and PS2 having a feeding variable speed control circuit for controlling an arc length by performing variable speed control of feeding speeds Fw1 and Fw2 of weld wires 11 and 12 are arranged in series to perform welding. Values of gains Gr1 and Gr2 of the feeding variable speed control circuit are set smaller in the following submerged arc welding apparatus PS2 than in the foremost submerged arc welding apparatus PS1.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a multi-electrode submerged arc welding system in which a plurality of submerged arc welding devices each having a variable feed speed control are arranged in series to perform welding. [Background technology]

[0002] A submerged arc welding method has been disclosed in which the arc length can be controlled by variable feed speed control that changes the feed speed of the welding wire in response to the welding voltage (see, for example, Patent Document 1).

[0003] In variable feed speed control, the welding voltage, which correlates with the arc length, is maintained at an appropriate value by feedback-controlling the feed speed based on the error between the detected value and the set value of the welding voltage. In submerged arc welding using a thick wire, the wire melting rate is unlikely to change even if the welding current changes, so it is difficult to obtain the self-regulation of the arc length that is generally used in consumable electrode arc welding using a welding power source with constant voltage characteristics. For this reason, in submerged arc welding, the arc length is maintained at an appropriate value by performing variable feed speed control using a welding power source with constant current characteristics.

[0004] In the variable feed speed control, when the detected value of the welding voltage is greater than the set value, the arc length is longer than the set value, so the feed speed is accelerated to shorten the arc length and bring it closer to the set value. Conversely, when the detected value of the welding voltage is less than the set value, the arc length is shorter than the set value, so the feed speed is decelerated to lengthen the arc length and bring it closer to the set value. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 9-271944 Summary of the Invention [Problem to be solved by the invention]

[0006] A multi-electrode submerged arc welding system is commonly used in which a plurality of submerged arc welding apparatuses, each equipped with a variable feed speed control circuit that controls the arc length by variably controlling the feed speed of the welding wire, are arranged in series for welding. In welding using the multi-electrode submerged arc welding system, there is a problem that the feed speed frequently fluctuates due to the variable feed speed control installed in the subsequent submerged arc welding apparatus, resulting in an unstable welding state.

[0007] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a multi-electrode submerged arc welding system capable of stabilizing the welding condition by a trailing submerged arc welding device. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the invention of claim 1 comprises: In a multi-electrode submerged arc welding system, a plurality of submerged arc welding devices each having a variable feed speed control circuit that controls an arc length by variably controlling a welding wire feed speed are arranged in series to perform welding, a gain of the variable feed speed control circuit of the subsequent submerged arc welding device is set to a value smaller than that of the leading submerged arc welding device; The present invention relates to a multi-electrode submerged arc welding system.

[0009] The invention of claim 2 is as follows: The submerged arc welding apparatus includes a gain setter for manually setting the gain. 2. The multi-electrode submerged arc welding system according to claim 1 .

[0010] The invention of claim 3 is as follows: The variable feed speed control circuit controls the feed speed including reverse feed. 3. A multi-electrode submerged arc welding system according to claim 1 or 2. Effect of the Invention

[0011] According to the submerged arc welding system of the present invention, the welding state by the following submerged arc welding device can be stabilized, so that the welding quality can be improved. [Brief description of the drawings]

[0012] [Figure 1] 1 is a configuration diagram of a multi-electrode submerged arc welding system according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram of the first and second submerged arc welding devices of FIG. 1. [Diagram 3] FIG. 4 is a waveform diagram of a welding current Iw and a welding voltage Vw. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] 1 is a configuration diagram of a multi-electrode submerged arc welding system according to an embodiment of the present invention. Each component will be described below with reference to the drawings.

[0015] The multiple electrode submerged arc welding system is configured with two to four submerged arc welding devices arranged in series, and the figure shows the case of two devices. The leading first submerged arc welding device is equipped with a first welding power source PS1, a first feeder WM1, a first welding torch 41, a first gain setter GR1, and a flux feeder 6. The trailing second submerged arc welding device is equipped with a second welding power source PS2, a second feeder WM2, a second welding torch 42, and a second gain setter GR2.

[0016] [Configuration of the first submerged arc welding device] The first gain setter GR1 is provided on the front panel of the first welding power source PS1, and outputs a first gain setting signal Gr1 that is manually set by a welding operator. The first welding power source PS1 receives the first gain setting signal Gr1 as an input, sets a gain for variable feed speed control by the first gain setting signal Gr1, and outputs a first feed control signal Fc1 for controlling a first feed speed Fw1 of the first welding wire 11 by the variable feed speed control, and also outputs a first welding current Iw1 and a first welding voltage Vw1. The first welding power source PS1 will be described in detail later with reference to FIG. 2. The first feeder WM1 receives the first feed control signal Fc1 as an input, and feeds the first welding wire 11 at a first feed speed Fw1. The first welding wire 11 is fed through the first welding torch 41, and a first arc 31 is generated between the first welding wire 11 and the base metal 2. A first welding voltage Vw1 is applied between a power feed tip (not shown) of first welding torch 41 and base material 2, and a first welding current Iw1 flows. Flux (not shown) is sprayed from flux supplier 6 so as to cover first arc 31. First arc 31 cannot be seen from the outside because it is covered by flux, but is shown as a see-through view in the figure.

[0017] [Configuration of the second submerged arc welding equipment] The second gain setter GR2 is provided on the front panel of the second welding power source PS2, and outputs a second gain setting signal Gr2 that is manually set by a welding operator. The second welding power source PS2 receives the second gain setting signal Gr2, sets a gain for variable feed speed control by the second gain setting signal Gr2, and outputs a second feed control signal Fc2 for controlling a second feed speed Fw2 of the second welding wire 12 by variable feed speed control, and outputs a second welding current Iw2 and a second welding voltage Vw2. Details of the second welding power source PS2 will be described later with reference to FIG. 2. The second feeder WM2 receives the second feed control signal Fc2, and feeds the second welding wire 12 at the second feed speed Fw2. The second welding wire 12 is fed through the second welding torch 42, and a second arc 32 is generated between the second welding wire 12 and the base metal 2. A second welding voltage Vw2 is applied between a power feed tip (not shown) of second welding torch 42 and base metal 2, and a second welding current Iw2 flows. Second arc 32 is covered with flux and cannot be seen from the outside, but is shown as a see-through view in the figure.

[0018] The inter-electrode distance between first welding wire 11 and second welding wire 12 is about 10 to 50 mm. First welding torch 41 and second welding torch 42 are mounted on an automatic cart (not shown) or a welding robot (not shown) and move along the weld line.

[0019] The value of the second gain setting signal Gr2 is set to a value smaller than the value of the first gain setting signal Gr1. That is, the gain of the variable feed speed control of the trailing submerged arc welding device is set to a value smaller than that of the leading submerged arc welding device.

[0020] Fig. 2 is a block diagram of the first and second submerged arc welding devices in Fig. 1. Each block will be described below with reference to the drawing.

[0021] The main power supply circuit PM is connected to a commercial power supply (not shown) such as a three-phase 200V power supply, and receives as input a current error amplification signal Ei (described later) and a polarity switching signal Spn (described later), performs inverter control in accordance with the current error amplification signal Ei, and switches between electrode positive polarity EP and electrode negative polarity EN in accordance with the polarity switching signal Spn to output AC welding current Iw and welding voltage Vw. Although not shown, this power supply main circuit PM includes a primary rectifier that rectifies the commercial power supply, a smoothing capacitor that smoothes the rectified DC, a primary-side inverter circuit that converts the smoothed DC into high-frequency AC, a high-frequency transformer that steps down the high-frequency AC to a voltage value suitable for welding, a secondary rectifier that rectifies the stepped-down high-frequency AC into DC, a reactor that smoothes the rectified DC, a secondary-side inverter circuit that switches the smoothed DC between electrode positive polarity EP and electrode negative polarity EN in accordance with a polarity switching signal Spn, a modulation circuit that receives as input the current error amplified signal Ei and outputs a pulse-width modulated signal, and a drive circuit that receives as input the pulse-width modulated signal to drive the switching elements of the primary-side inverter circuit.

[0022] The welding wire 1 is fed through the welding torch 4 by the rotation of a feed roll 5 coupled to a feeder WM, and an arc 3 is generated between the welding wire 1 and the base material 2. A welding voltage Vw is applied between a power feed tip (not shown) of the welding torch 4 and the base material 2, and a welding current Iw flows. A flux feeder 6 is disposed in the first submerged arc welding device, and supplies flux (not shown) to the arc generating part. The arc generating part is covered by the flux, so that the arc 3 cannot be seen from the outside. The welding torch 4 is mounted on an automatic cart, a welding robot, or the like, and moves along the weld line.

[0023] The current detection circuit ID detects the instantaneous value of the AC welding current Iw, converts it into an absolute value, and outputs a current detection signal Id.

[0024] The RMS current detection circuit IED receives the current detection signal Id, calculates an effective value from the current detection signal Id, and outputs an RMS current detection signal Ied. The RMS current setting circuit IER outputs a predetermined RMS current setting signal Ier. The current amplitude modulation circuit AMC receives the RMS current detection signal Ied and the RMS current setting signal Ier, performs modulation control based on the error amplification value of both values, and outputs a current amplitude modulation signal Amc. This circuit changes the amplitude of the welding current Iw so that the effective value of the welding current Iw becomes equal to the set value.

[0025] The electrode positive polarity period setting circuit TPR outputs a predetermined electrode positive polarity period setting signal Tpr, and the electrode negative polarity period setting circuit TNR outputs a predetermined electrode negative polarity period setting signal Tnr.

[0026] The current setting circuit IR receives the electrode positive polarity period setting signal Tpr, the electrode negative polarity period setting signal Tnr, and the current amplitude modulation signal Amc as inputs, performs the following processes 1) to 3), and outputs a current setting signal Ir having a half-sine waveform, as well as a polarity switching signal Spn for switching the power supply polarity. 1) During the electrode positive polarity period Tep set by the electrode positive polarity period setting signal Tpr, the start and end points of the period become the polarity switching current value, and a half-wave sine wave having an amplitude set by the current amplitude modulation signal Amc is output as the current setting signal Ir. During the electrode positive polarity period Tep, a polarity switching signal Spn that is at a High level is output. 2) During the electrode negative polarity period Ten set by the electrode negative polarity period setting signal Tnr, the start and end points of the period are the polarity switching current value, and a half-sine wave waveform with an amplitude set by the current amplitude modulation signal Amc is output as the current setting signal Ir. During the electrode negative polarity period Ten, a polarity switching signal Spn that is at a low level is output. 3) Repeat steps 1) and 2) above.

[0027] The current error amplifier circuit EI receives the current setting signal Ir and the current detection signal Id, amplifies the error between the two values, and outputs a current error amplified signal Ei. This circuit controls the welding device to have a constant current.

[0028] The voltage detection circuit VD detects the effective value of the AC welding voltage Vw and outputs a voltage detection signal Vd. The voltage detection signal Vd is a value that correlates with the arc length, so it detects the arc length. The voltage setting circuit VR outputs a predetermined voltage setting signal Vr for setting the desired arc length.

[0029] The gain setter GR is provided on the front panel of the welding power source and outputs a gain setting signal Gr that is manually set by a welding operator. Here, the value of the gain setting signal Gr of the second submerged arc welding device is set to a value smaller than the value of the gain setting signal Gr of the first submerged arc welding device. In other words, the gain of the variable feed speed control of the trailing submerged arc welding device is set to a value smaller than that of the leading submerged arc welding device.

[0030] The variable feed speed control circuit FMC receives the voltage detection signal Vd, the voltage setting signal Vr, and the gain setting signal Gr as inputs, performs variable feed speed control as described below based on the error between the voltage detection signal Vd and the voltage setting signal Vr and the gain setting signal Gr, and outputs a feed speed modulation signal Fmc. 1) The variable feed speed control performs P (proportional) control, PI (proportional-integral) control or PID (proportional-integral-derivative) control based on the error and gain setting signal Gr, and changes the value of the feed speed modulation signal Fmc to increase (acceleration), decrease (deceleration) or decrease to a negative value (reverse feed speed). 2) Preferably, the variable feed speed control varies the value of the feed speed modulation signal Fmc, including decreasing it to a negative value (reverse feed speed), when the voltage detection signal Vd is smaller than the voltage setting signal Vr. 3) More preferably, the variable feed speed control reduces the value of the feed speed modulation signal Fmc to a negative value (reverse feed speed) when the absolute value of the error is equal to or greater than a reference value when the voltage detection signal Vd is smaller than the voltage setting signal Vr.

[0031] The feed control circuit FC receives the feed speed modulation signal Fmc and outputs a feed control signal Fc to the feeder WM for controlling the feed speed Fw of the welding wire 1 to a speed determined by the feed speed modulation signal Fmc.

[0032] 3 is a waveform diagram of the welding current Iw and the welding voltage Vw, in which positive values ​​above 0 A and 0 V correspond to the electrode positive polarity EP, and negative values ​​below 0 V correspond to the electrode negative polarity EN.

[0033] As shown in FIG. 1A, during an electrode positive polarity period Tep from time t1 to t2, the welding current Iw has a positive polarity switching current value at the start point t1 and end point t2 of the period, and has a positive half-wave waveform of a sine wave with an amplitude set by the current amplitude modulation signal Amc. As shown in FIG. 1A, during an electrode negative polarity period Ten from time t2 to t3, the welding current Iw has a negative polarity switching current value at the start point t2 and end point t3 of the period, and has a negative half-wave waveform of a sine wave with an amplitude set by the current amplitude modulation signal Amc. The electrode positive polarity period Tep is set by the electrode positive polarity period setting signal Tpr in FIG. 1. The electrode negative polarity period Ten is set by the electrode negative polarity period setting signal Tnr in FIG. 1. The amplitude is modulated and controlled so that the current effective value detection signal Ied in FIG. 1 is equal to the current effective value setting signal Ier. For example, Tep=10 ms, Ten=10 ms, polarity switching current value=±200A, and amplitude=±1000A.

[0034] As shown in Fig. 1B, the welding voltage Vw has a waveform similar to a square wave. The effective value of the welding voltage Vw is a value that correlates with the arc length.

[0035] The effects of this embodiment will be described below. According to this embodiment, in a multi-electrode submerged arc welding system in which a plurality of submerged arc welding devices each having a variable feed speed control circuit for controlling the arc length by controlling the variable speed of the welding wire are arranged in series, the gain of the variable feed speed control circuit is set to a smaller value for the trailing submerged arc welding device than for the leading submerged arc welding device. The welding state by the trailing submerged arc welding device has a larger fluctuation in the molten pool than the welding state by the leading submerged arc welding device, so that the apparent arc length fluctuates frequently. Even if the apparent arc length fluctuates due to the fluctuation in the molten pool, the average value of the arc length hardly fluctuates, so that the adverse effect on the welding quality is small. Therefore, it is not necessary to change the feed speed in response to the fluctuation in the apparent arc length due to the fluctuation in the molten pool. However, if the gain of the variable feed speed control is set to a large value, the feed speed will change frequently in response to the fluctuation in the molten pool, which will cause the welding state to become unstable. For this reason, the above problem can be suppressed by setting the gain of the variable feed speed control of the trailing submerged arc welding device to a value smaller than that of the leading submerged arc welding device, whereas the fluctuation in arc length can be suppressed by setting the gain of the variable feed speed control of the leading submerged arc welding device to a value larger than that of the trailing submerged arc welding device, thereby stabilizing the welding state.

[0036] More preferably, according to this embodiment, the submerged arc welding apparatus includes a gain setter for manually setting the gain. In this way, the welding operator can easily manually set appropriate gains for each of the leading and trailing submerged arc welding apparatuses. As a result, the arc length can be maintained at an appropriate value by variable feed speed control of each submerged arc welding apparatus, thereby improving welding quality.

[0037] More preferably, according to this embodiment, the variable feed speed control circuit controls the feed speed including the reverse feed. When the arc length varies in the direction of increasing the length during welding, the value of the voltage detection signal becomes larger than the value of the voltage setting signal, and the feed speed is transiently accelerated. As a result, the melting speed of the welding wire becomes smaller than the feed speed, so the arc length becomes shorter and returns to the set value. When the arc length varies in the direction of decreasing a small amount during welding, the value of the voltage detection signal becomes smaller than the value of the voltage setting signal, and the feed speed is transiently decelerated. As a result, the melting speed of the welding wire becomes larger than the feed speed, so the arc length becomes longer and returns to the set value. When the arc length varies in the direction of decreasing a large amount during welding, the value of the voltage detection signal becomes larger than the value of the voltage setting signal, and the feed speed is transiently reversed. As a result, the tip of the welding wire is directly pulled up, so the arc length quickly increases and returns to the set value. As described above, in this embodiment, even if the arc length fluctuates in the direction of increasing or decreasing the length, the feed speed is accelerated, decelerated, or reversed, so that the arc length can be quickly returned to the set value. [Explanation of symbols]

[0038] 1 Welding wire 11 First welding wire 12 Second welding wire 2 Base material 3. Arc 31 1st Arc 32 2nd Arc 4. Welding torch 41 No. 1 Welding Torch 42 No. 2 welding torch 5 Feeding roll 6 Flux supply machine AMC Current Amplitude Modulation Circuit Amc Current Amplitude Modulation Signal EI Current Error Amplifier Circuit Ei Current error amplification signal EN Electrode negative polarity EP electrode positive polarity FC feed control circuit Fc feed control signal FMC Variable speed feed control circuit Fmc Feed speed modulation signal Fw Feed speed Fw1 1st feed speed Fw2 2nd feed speed GR Gain setting circuit Gr Gain setting signal GR1 First gain setting circuit Gr1 1st gain setting signal GR2 Second gain setting circuit Gr2 Second gain setting signal ID Current Detection Circuit Id Current detection signal IED Current Effective Value Detection Circuit Ied Current effective value detection signal IER Current effective value setting circuit Ier Current effective value setting signal IR current setting circuit Ir Current setting signal Iw Welding current Iw1 First welding current Iw2 Second welding current PM power supply main circuit SPN polarity switching signal Ten electrode negative polarity period Tep electrode positive polarity period TNR Electrode negative polarity period setting circuit Tnr Electrode negative polarity period setting signal TPR electrode positive polarity period setting circuit Tpr electrode positive polarity period setting signal VD voltage detection circuit Vd Voltage detection signal VR voltage setting circuit Vr Voltage setting signal Vw welding voltage Vw1 First welding voltage Vw2 Second welding voltage WM feeder WM1 1st feeder WM2 2nd feeder

Claims

1. In a multi-electrode submerged arc welding system, a plurality of submerged arc welding devices each having a variable feed speed control circuit that controls an arc length by variably controlling a welding wire feed speed are arranged in series, a gain of the variable feed speed control circuit of the subsequent submerged arc welding device is set to a value smaller than that of the leading submerged arc welding device; A multi-electrode submerged arc welding system comprising:

2. The submerged arc welding apparatus includes a gain setter for manually setting the gain.

2. The multi-electrode submerged arc welding system according to claim 1.

3. The variable feed speed control circuit controls the feed speed including reverse feed.

3. A multi-electrode submerged arc welding system according to claim 1 or 2.

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